Fuse plug



Jan. 18, 1938. PRENDER AS 2,106,109

FUSE PLUG Filed June 4; 1936 INVENTOR @Zm W fi V r? .3?" l VIM Patented Jan. 18, 1938 UNITED STATES PATENT OFFICE Application June 4,

9 Claims.

My invention relates in general to fuse plugs and is particularly applicable to a multiple-fuse plug so arranged that a portion of the plug may be turned so that a new section of the fuse ele- 5 ment may be engaged after one fuse section has been melted out by a short circuit or by over load on the line, thereby eliminating the necessity of removing the plug and inserting a new one in order to make the circuit operative.

By my invention, I provide a fuse plug which may be readily placed in the circuit and which may be conveniently and quickly manipulated to place a new section of the fuse element in the circuit as the occasion arises.

Heretofore, attempts have been made to provide a suitable multiple-fuse plug, but, insofar as I am aware no one has been successful. One of the serious draw-backs has been the tendency to a fuse all of the elements at once, which draw-back J I have overcome. A fuse plug made according to my invention is perfectly reliable, safe, and positive in operation and may be produced in an economical manner. The plug is so insulated that there will be no possibility of a short circuit occurring therein or of more than one section of the fuse element blowing out at the same time.

The fuse plug is provided with a rotatable cap member and secured therein is a fusible member having a plurality of arms, any one of which may be connected into the circuit so that in the event of one of said arms blowing, another arm may be moved into circuit closing position. This operation may be repeated as often as is necessary or until all the arms in succession have been blown. By inspection through the cap member, one can readily determine which arm of the fuse element has blown. The cap is provided with means to prevent it turning in any out the proper direction, which means also assure that the elements are in the correct operative position which can be determined audibly and by touch. Post--- tive contact between the end of the plug and the socket in which it is placed is also provided for.

Provision is also made for preventing arcing -5 when a fuse blows, which arcing is particularly liable to occur when the fuse is employed for protecting circuits carrying currents of the order of twenty amperes and upwards. The fuse made according to my invention provides a combustion chamber of such size that the pressure within the chamber during combustion is insuiiicient to rupture the fuse plug body.

My fuse plug, although capable of repeated use, because of its multiple character need be no larger in size than the ordinary fuse plug of commercial use, and may be manufactured at a low cost, so that a fuse plug having the life of eight ordinary plugs will cost about the same as the single fuse plug now in common use. The fuse plug may be utilized in the customary way and in 1936, Serial N0. 83,462

the customary sockets so that it is unnecessary to change the wiring fixtures. The plug as a whole need be rep-laced only after all of the fuse elements have been blown.

In the drawing, I have illustrated a present preferred embodiment of my invention and therein corresponding and like parts are designated by like reference numerals.

Figure 1 is a side elevation of the fuse plug complete;

Figure 2 is a cross-section on the line II-II of Figure 1;

Figure 3 is a plan View of the plug with the rotatable cap removed;

Figure 4 is a bottom plan view of the rotatable p;

Figure 5 is a cross-section on the line V-V of Figure 4;

Figure 6 is a plan view of the multiple fuse element before it is inserted in the cap;

Figure 'l is a plan view of the indicating memher; and

Figure 8 is a view in perspective of the sealing member.

In the drawing, there is shown a body member 2 and a cap member or fuse carrier 3, both of which are made from non-conducting material, such as porcelain, fibre, synthetic resin, or the like. Preferably, the cap member is transparent.

The body member 2 includes at one end a reduced portion 4, to which is applied a threaded metallic sleeve 5 for screwing into the ordinary Edison socket, and at the other end a cup'shaped portion 6, in which is a depression or recess l. The threaded sleeve or shell 5 has a plurality of arms or extensions 3, which pass through openings 9 into the recess 1 where they are secured to the arcuate contact member it positioned in the recess. This contact member It is formed from resilient metal and has an upwardly turned end H, which engages in turn the ends or arms of the metal fusible element later to be described. For ease in assembling there is formed in the reduced portion 4, the grooves l2, one for each arm ii. The grooves l2 connect with the openings 9.

Inside the recess 1 is a centrally located boss 23 and extending axially through this boss and through thebody member or insertible portion 2 is a bore M, through which slidably extends a metal pin or rod 15. To the lower end of this rod, a U-shaped contact member 16 of resilient metal is secured and between the enlarged head H of the other end of rod l5 and the top of boss l3, a spring i8 is positioned. Rod [5 is of such length that when the plug is assembled the spring I8 is compressed to a slight extent so that positive contact between the head l1 and the fuse element is maintained. One arm of the U-shaped contact member 16 is received in a depression 19 in the lower or inner end of body member 2.

The cap member 3 formed preferably of glass or other transparent insulating material by molding or casting has a depression, well, or cavity 20, which extends into the cap from which cavity, radial notches or grooves 25 extend, in which the arms of the fuse elements are received. The radial notches 2! are separated from one another by partitions 22, which extend somewhat beyond the end or lower edge of the outside wall 23 of the cap member, so that between each pair of partitions there is along the lower edge of the wall depressed portions or recesses 24. t will be observed that the edges 22a of the partitions 22 adjacent the recesses 24 are rounded so that the end H of contact member EU will ride smoothly out of the recesses 24 between the partitions. The edges of the partitions adjacent the other side of the recesses 2d are substantially vertical. By this arrangement, the cap member may be rotated in one direction only, for example, clockwise as shown. Furthermore, the end ll of contact member l0 when it drops into the depressed portion 24 makes an audible click and positive contact with an arm of the fusible element.

A ridge or flange extends circiunferentially from the outside of the cap member at a convenient location between the top and bottom thereof. In the top or outside of the cap member 3, a depression 2s is provided, the shape of which depends on the Fire Underwriters requirements. The outside of the cap member between the ridge 25 and the top or outside of the cap member is serrated, so that the member may be gripped for turning,

The fuse element 2'1", see Figure 6, is formed in the shape of a rimless wheel and has a. hub portion 28 having radial elements 29, extending therefrom. These elements have a hub contacting portion 30, blow-out reduced area portions 3: and contact portions 32, which are of greater cross-sectional area than the blow-out portions. The contact portions 32 are preferably necked as shown at 33, as an aid in assembling the fuse plugs. It is, of course, understood that the con tact portion need not be necked to make satisfactory fuse and that the contact portion 32 may be of uniform cross-section. The fuse is of such dimension that the ends or" the radial arms will pass through the notches 2i beyond recess 24, and extend part way on the flange The outer ends of the arms are retained in position by a washer 34 of non-conducting material, preferably fibre, which makes close fit with the outside of the cap member and rests against the lower side of flange 25.

The sealing member see Figure 8, consists of a sleeve 36 from the sides of which radial pro-- jections 31 extend, so spaced and of a size to be received in the notches Si in the cap member The sleeve 36 is long enough to extend. from the bottom of the fuse cavity 2! in the cap member to and part way along the boss i3. The radial projections 37 are so arranged on the sleeve that they close the outer ends of the notches 2i and lie below the outer edges of the partitions 22. The sealing member 35 is made from a nonconducting material and preferably from one that can be performed as by molding or casting. I have found that rubber is satisfactory and so also is bakelite and fibre, but I do not wish to be confined to the use of these materials. The sleeve 33 is closely fitted to the ends of the partitions 2;. so-that each notch 2i forms a chamber by itself.

Since the notches 2| are closed at their outer ends, but not gas tight, by projections 31 gas chambers or combustion chambers are formed wherein the gases generated by the blowing fuses may expand without developing enough pressure to disrupt the fuse plug, and wherein any resulting flame is confined. The assembly is not gas tight, so that the gases may be dispersed into the surrounding atmosphere without any harmful result.

The signal member or indicator 38, Figure '7, has a hub portion 39 and radial arms 40 extending therefrom. The member is made from paper and the side which faces the top of the cap memher 3 is colored red and has a number thereon denoting the ampere capacity of the fuse. The member is of such size that it fits snugly into cavity 20 of cap member 2 and the radial arms 40 thereof extend into the notches 2| of the cap member. When the fuse in the same notch as the corresponding arm of the signal member is blown, the radial arm is discolored, thus showing which fuse arm has blown out. It is also possible to color the side of the fuse element which is visible from the top of the plug so that the burned arm will show up clearly, in which case the indicator 33 could be omitted.

The cap member is assembled by placing a signal member 38 inside the cavity 2!, colored side uppermost. The fuse element 21 is then inserted in the cap so that the hub portion is received in the cavity and the radial extending arms are received in the notches 2|, the ends of the arms extending around the ledges 24 where they are secured in position by means of the fibre washer 34. The sealing member 35 is then placed in position in the cap. The cap member is next placed over the body member, as illustrated in Figure 2, and is rotatably secured thereto by an annular ring 4!, which has a flange portion 42 to engage the upper side of ridge 25. The ring is secured to the body member, for example, by crimping a. portion of the ring into grooves or recesses 43 in the body member.

While I have illustrated and described a preferred embodiment of my invention, it will be understood that the invention is not limited thereto and that various changes in the shape, size, numher, and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the following claims.

I claim:

1. In a multiple-fuse plug, a body member, a cap member rotatably carried on the body member, said cap member having an inverted well therein, the outer walls of which are provided with radially extending recesses, a fuse member having a hub portion located against the bottom of the well, radial arms with reduced area portions connected to said hub and located in the recesses and extending vertically to the top of the recesses and being turned over the edge of the well, and a hollow sleeve member fitted in the well having radial projections fitting into the said radial recesses, the radial extensions of the fuse member having a part of the vertical portion thereof of reduced area.

2. In a multiple-fuse plug, a body member, a cap member rotatably carried on the body memher, said cap member having an inverted well therein, the outer walls of which are provided with radially extending recesses, a fuse member having a hub portion located against the bottom of the well, radial arms with reduced area portions connected to said hub and located in the recesses and eidsending vertically to the top of the recesses and being turned over the edge of the well, and a hollow sleeve member fitted in the well in contact with the inner edge portions of the cap member forming the recesses and having radial projections fitting into the said radial recesses, the radial extensions of the fuse member having a part of the vertical portion thereof of reduced area.

3. In a multiple-fuse plug, a body member, a cap member rotatably carried on the body member, said cap member having an inverted wall therein, the outer walls of which are provided with radially extending recesses, a fuse member having a hub portion located against the bottom of the well, radial arms with reduced area portions connected to said hub and located in the recesses and extending vertically to the top of the. recesses and being turned over the edge of the well, a hollow sleeve member fitted in the well having radial projections fitting into the said radial recesses, the radial extensions of the fuse member having a part of the vertical portion thereof of reduced area, and a contact member passing through said hollow sleeve and engaging the hub portion of the fuse member.

4. In a multiple-fuse plug, a body member, a cap member rotatably carried on the body member, said cap member having an inverted well therein, the outer walls of which are provided with radially extending recesses, a fuse member having a hub portion located against the bottom of the well, radial arms with reduced area portions connected to said hub and located in the recesses and extending vertically to the top of the recesses and being turned over the edge of the well, and a cylindrical sleeve of insulating material fitted into the well for closing communication from one recess to another, the radial extensions of the fuse member having a part thereof of reduced area.

5. In a multiple-fuse plug, a body member, a cap member rotatably carried on the body member, said cap member having an inverted well therein, the outer walls of which are provided with radially extending recesses, a fuse member having a hub portion located against the bottom of the well, radial arms with reduced area portions connected to said hub and located in the recesses and extending vertically to the top of the recesses and being turned over the edge of the well, and a cylindrical sleeve of insulating material fitted into the well for closing communication from one recess to another, the radial extensions of the fuse member having a part thereof of reduced area, said cap member having a laterally turned flange and a non-conducting washer on said flange engaging the outer extremities of the radial arms.

6. In a multiple fuse plug, a body member having an axial bore therethrough, a threaded screw contact on the body member, a resilient contact movably extending through said bore, a cap member rotatably mounted on the body member and having a centrally located cavity and radial notches extending from said cavity in which is received a fuse element having a hub portion located against the bottom of the cavity and radial elements having reduced area portions connected to the hub portion and extending into the notches, said hub portion contacting said resilient contact, means whereby the outer portions of said radial elements may be successively electrically connected to the screw contact, and means whereby the sides and outer ends of said radial notches may be closed so as to form combustion chambers for the reduced area portions of the fuse element.

7. In a multiple fuse plug, a body member having an axial bore therethrough, a threaded screw contact on the body member, a second contact extending through said bore, a cap member rotatably mounted on the body member and having a central cavity and radial notches extending therefrom in which is received a fuse element having a hub portion which contacts the bottom of the cavity and radial elements having reduced area portions connected to the hub portion, said hub portion contacting said second contact, means whereby the outer portions of said radial elements may be successively electrically connected to the screw contact, a cylindrical member located in said cavity for closing the radial notches so as to form combustion chambers for the reduced area portions of the fuse element, said member having radial projections thereon which close the ends of the notches, said closing member being made of non-conducting material, and means whereby the outer extremities of the radial elements may be secured in position on the cap.

8. In a multiple fuse plug, a body member tion with one of the contacts of the receptacle, 1

resilient means for connecting the portions of the radial arms distant from the ends thereof and beyond the reduced area portions to the other contact of the receptacle, said reduced area portions being confined in separate combustion chambers, and means mounted on the cap for holding the outer extremities of the arms against movement.

9. In a multiple fuse plug, a body member formed cup-shaped at one end, a cap member rotatably received in the cup-shaped portion and having a central cavity with radial notches extending therefrom, a contact member secured in the base of said cup-shaped portion and having an outwardly turned resilient end portion, a fuse element carried by said cap member and having a hub portion located against the bottom of the cavity and radial elements having reduced area portions connected tothe hub portion, the radial elements passing through the notches and over depressions in the edge of the cap member, said portions in the depressions being successively engageable upon rotation of said cap member with the outwardly turned portion of said contact member, means closing the ends and sides of said radial notches, said depressions and contact member being arranged so that the cap may be rotated in one direction only, and means mounted on the cap to hold the extremities of the radial arms securely in position.

PIERCE PRENDERGAST. 

